Oil-in-water emulsions

ABSTRACT

The invention relates to oil-in-water emulsions based on fatty alcohols and the use thereof as antifoams or deaerators for aqueous compositions. Such oil-in-water emulsions consist to at least 95% by weight of the following constituents:
     a) 50 to 80% by weight, in particular 55 to 75% by weight and specifically 60 to 70% by weight, based on the total weight of the oil phase, of at least one alkanol having at least 16 carbon atoms, in particular having 16 to 20 carbon atoms, where the fraction of alcohols having 16 to 18 carbon atoms constitutes at least 80% by weight, in particular 90% by weight, specifically 95% by weight or at least 99%, based on the total amount of component A,   b) 1 to 10% by weight, in particular to 2 to 8% by weight, specifically 3 to 6% by weight, based on the total weight of the oil phase, of at least one further component B, which is selected from esters of C 12 -C 36 -alkanecarboxylic acids with polyglycerol and esters of C 12 -C 36 -alkanecarboxylic acids with C 12 -C 36 -alkanols, and mixtures thereof,   c) 10 to 49% by weight, in particular 20 to 40% by weight, specifically 25 to 35% by weight, based on the total weight of the oil phase, of at least one further component C, which is selected from organic substances which are liquid at 50° C. and 1013 mbar, at atmospheric pressure have a boiling point above 200° C., and at 25° C. and 1013 mbar have a solubility in water of less than 0.1 g/l.

The invention relates to oil-in-water emulsions based on fatty alcoholsand to the use thereof as antifoams or deaerators for aqueouscompositions.

In numerous industrial processes, it is necessary to handle aqueoussolutions and suspensions which have a tendency toward foam formation onaccount of their ingredients. This foam formation makes the processdifficult to carry out and therefore has to be kept as low as possibleor avoided altogether. Examples of foam-forming aqueous compositions aredetergent-comprising compositions, saponin-comprising compositions,wastewater in water treatment plants, protein-comprising compositionssuch as soybean extracts and in particular paper stock suspensions, e.g.groundwood-and/or cellulose-comprising suspensions, as are used inparticular in the paper industry for producing paper, board orcardboard.

Besides the formation of foam, which is permanently after-formed fromcoalescing air bubbles, the air incorporated in these systems, which isin a finely dispersed, stable form, also proves to be problematical. Thereduction in the air content of these systems is therefore likewise ofparticular importance.

For these reasons, so-called antifoams and/or deaerators are added tothe film-forming aqueous compositions during their processing andsometimes even during their production; these antifoams and/ordeaerators, even at low use concentrations, suppress the undesiredformation of foam, reduce the content of incorporated air or destroyfoam which has already been produced.

The antifoams known from the prior art are often aqueous compositionsbased on oil-in-water dispersions or emulsions, the oil phase of whichcomprises at least one hydrophobic substance, for example mineral oils,silicone oils, polyalkylene oxides, esters thereof with fatty acids andethers thereof with long-chain alcohols, native fats and/or oils, waxes,ester waxes or long-chain alcohols. Occasionally, the use ofdistillation residues which are formed during the production oflong-chain alcohols in accordance with the Ziegler process or during oxosynthesis has also been reported (see e.g. EP-A 149812).

U.S. Pat. No. 4,950,420 discloses antifoams for the paper industry whichcomprise 10 to 90% by weight of a surface-active polyether, such aspolyalkoxylated glycerol or polyalkoxylated sorbitol, and 10 to 90% byweight of a fatty acid ester of polyhydric alcohols, such as mono- anddiesters of polyethylene glycol or polypropylene glycol.

EP-A 531713 and WO 94/08091 describe antifoams for the paper industrybased on oil-in-water emulsions, the oil phases of which comprisealcohols, fatty acid esters, distillation residues, hydrocarbons incombination with polyglycerol esters.

DE 2157033 describes antifoams based on aqueous emulsions which compriseC₁₂-C₂₂-alkanols and/or C₁₂-C₂₂-fatty acid esters of di- to trihydricalcohols and paraffin oil or C₁₂-C₂₂-fatty acids.

Joshi et al. established in Colloids and Surfaces A: Physicochem. Eng.Aspects 263 (2005) 239-249 that the effectiveness of an antifoam basedon fatty alcohol depends on its aggregate state. The effectiveness ishighest if it is partly molten. This gives rise in the specialist fieldto the requirement to use mixtures of fatty acid alcohols which, beingmixtures, have a broader melting range than pure substances.

In the prior art, the effectiveness of an antifoam is often measured byits ability to suppress foam formation at a liquid surface. Particularlyin papermaking, however, it is also of importance to reduce the aircontent in the aqueous liquids produced during papermaking, particularlyin the paper stock suspensions. Antifoams which are likewise able to actas deaerators are not often described in the prior art. The knownantifoams often leave something to be desired with regard to thedeaerating effect, particularly at temperatures below 50° C., e.g. inthe range from 20 to <50° C.

The object of the present invention is to provide compositions whichhave high effectiveness both as antifoam and also as deaerator foraqueous compositions, in particular for aqueous paper stock suspensions.

These and other objects are achieved by oil-in-water emulsions, the oilphase of which consists to at least 95% by weight of the followingconstituents:

-   a) 50 to 80% by weight, in particular 55 to 75% by weight and    specifically 60 to 70% by weight, based on the total weight of the    oil phase, of at least one alkanol having at least 16 carbon atoms,    in particular having 16 to 20 carbon atoms, where the fraction of    alkanols having 16 to 18 carbon atoms constitutes at least 80% by    weight, in particular at least 90% by weight, specifically at least    95% by weight or at least 99%, based on the total amount of    component A,-   b) 1 to 10% by weight, in particular 2 to 8% by weight, specifically    3 to 6% by weight, based on the total weight of the oil phase, of at    least one further component B, which is selected from esters of    C₁₂-C₃₆-alkanecarboxylic acids with polyglycerol and esters of    C₁₂-C₃₆-alkanecarboxylic acids with C₁₂-C₃₆-alkanols, and mixtures    thereof,-   c) 10 to 49% by weight, in particular 20 to 40% by weight,    specifically 25 to 35% by weight, based on the total weight of the    oil phase, of at least one further component C, which is selected    from organic substances which are liquid at 50° C. and 1013 mbar, at    atmospheric pressure have a boiling point above 200° C., and at    25° C. and 1013 mbar have a solubility in water of less than 0.1    g/l.

Component A consists in particular of essentially unbranched alkanolshaving at least 16, in particular 16 to 20, carbon atoms, i.e. saturatedalcohols having at least 16, in particular 16 to 20, carbon atoms, inwhich the fraction of alcohols having 16 to 18 carbon atoms constitutesat least 80% by weight, in particular at least 90% by weight,specifically at least 95% by weight or at least 99%, based on the totalamount of component A, and which are linear to at least 80%, inparticular at least 90% and specifically at least 95%. Such linearalkanols can be described by the following formula:

H—(CH₂)_(n)—OH

in which n is an integer of at least 16 and in particular is in therange from 16 to 20. The fraction of alkanols, in particular linearalkanols having 16 to 18 carbon atoms, in particular having 16 or 18carbon atoms, is according to the invention at least 80% by weight, inparticular at least 90% by weight, specifically at least 95% by weightor at least 99% by weight, based on the total weight of component A.Examples of alcohols suitable as component A are palmityl alcohol (cetylalcohol), 1-heptadecanol, stearyl alcohol, arachyl alcohol(n-eicosanol), behenyl alcohol and mixtures thereof. Preferably,component A consists to at least 80%, in particular at least 90% andspecifically at least 95%, of palmityl alcohol, stearyl alcohol ormixtures thereof.

According to the invention, component A comprises less than 20% byweight, based on component A, of alcohols having more than 18 carbonatoms. Preferably, component A comprises less than 10% by weight, inparticular less than 5% by weight, specifically less than 1% by weightor less than 0.5% by weight, based on component A, of alcohols havingmore than 18 carbon atoms.

In a likewise preferred embodiment, palmityl alcohol or stearyl alcoholor a mixture of these alcohols is used as component A whereas componentA is free (less than 0.5% by weight, based on component A) from alcoholshaving more than 18 carbon atoms.

According to the invention, the fraction of component A in the oil phaseis 50 to 80% by weight, preferably 55 to 75% by weight, in particular 60to 70% by weight, based on the total weight of the oil phase.

Component B is selected from esters of alkanecarboxylic acids withpolyglycerol, esters of alkanecarboxylic acids with alkanols andmixtures thereof.

Esters of alkanecarboxylic acids with polyglycerol are understood asmeaning a polyglycerol esterified with at least one fatty acid which has12 to 36, in particular 16 to 30, specifically 18 to 24, carbon atoms.The fatty acids contemplated for the esterification of the polyglycerolmay either be saturated fatty acids or unsaturated fatty acids andmixtures thereof. Fatty acids suitable for the esterification of thepolyglycerol mixtures are preferably selected from saturated fatty acidshaving 12 to 36, in particular 16 to 30, specifically 18 to 24, carbonatoms. Examples of suitable saturated fatty acids are lauric acid,myristic acid, palmitic acid, stearic acid, arachic acid, behenic acidand montan wax acid. Examples of suitable unsaturated fatty acids areoleic acid, hexadecanoic acids, elaidic acid, eicosenoic acids anddocosenoic acids such as erucic acid or brassidic acid, and alsopolyunsaturated acids, such as octadecenedienoic acids and octatrienoicacids, such as linoleic acid and linolenic acid, and mixtures of thespecified saturated and unsaturated carboxylic acids. Preferably, thepolyglycerol is esterified with saturated carboxylic acids having 18 to24 carbon atoms, which are selected in particular from palmitic acid,stearic acid and behenic acid and mixtures thereof. In a specificembodiment, the polyglycerol ester is a polyglycerol esterified withbehenic acid.

The degree of esterification of the polyglycerol esters is generally 20to 100%, preferably 60 to 100%, based on the number of hydroxylfunctions in the polyglycerol.

Preferred polyglycerol esters are in particular those which areobtainable by esterifying polyglycerol mixtures which comprise 15 to 40%by weight of diglycerol, 30 to 55% by weight of triglycerol and 10 to25% by weight of tetraglycerol, in each case based on the total amountof the polyglycerol, where the total amount of di-, tri- andtetraglycerol constitutes at least 60% by weight, in particular at least80% by weight. In particular, mixtures with the following compositionare used for the esterification:

0 to 10% by weight of glycerol,15 to 40% by weight of diglycerol,30 to 55% by weight of triglycerol,10 to 25% by weight of tetraglycerol,0 to 15% by weight of pentaglycerol,0 to 10% by weight of hexaglycerol and0 to 5% by weight of more highly condensed polyglycerols.

In particular, the polyglycerol esters are those which are obtainable byesterifying one of the polyglycerol mixtures described above with atleast one saturated carboxylic acid having 18 to 24 carbon atoms, thecarboxylic acid being selected in particular from palmitic acid, stearicacid and behenic acid and mixtures thereof.

In the compositions according to the invention, particular preference isgiven to those polyglycerol esters which are obtainable by esterifyingbehenic acid with a polyglycerol mixture which consists of 0 to 10% byweight of glycerol, 15 to 40% by weight of diglycerol, 30 to 55% byweight of triglycerol, 10 to 25% by weight of tetraglycerol, 0 to 15% byweight of pentaglycerol, 0 to 10% by weight of hexaglycerol and 0 to 5%by weight of more highly condensed polyglycerols.

The polyglycerol mixtures used for the esterification are accessible forexample by alkaline catalyzed condensation of glycerol at elevatedtemperatures (cf. e.g. Fette, Seifen, Anstrichmittel, 88th volume, No.3, pages 101 to 106 (1986)) or as in DE-A 3842692 by reaction ofglycerol with epichlorohydrin in the presence of acidic catalysts atelevated temperatures. However, the mixtures are also obtainable bymixing together the pure polyglycerol components, e.g. diglycerol,triglycerol and tetraglycerol.

The polyglycerols esterified with alkanecarboxylic acids are known, e.g.from EP 531713 and WO 94/08091. They are typically prepared byesterification of polyglycerol, in particular by esterification of thepolyglycerol mixtures described above, with the desired fatty acid ormixture of fatty acids or ester-forming derivatives thereof, e.g.C₁-C₄-alkyl esters thereof, by methods known per se. As a rule, theprocedure is carried out in the presence of an acidic esterificationcatalyst such as sulfuric acid, p-toluenesulfonic acid, citric acid,phosphorous acid, phosphoric acid, hypophosphorous acid or basiccatalysts, such as sodium methylate or potassium tert-butylate.

Further suitable as component B are esters of C₁₂-C₃₆-alkanecarboxylicacids with C₁₂-C₃₆-alkanols. They are understood to include substanceswhich are obtainable by esterification of at least one, preferablysaturated, mono- to dibasic, preferably monobasic, alkanecarboxylic acidhaving 12 to 36, in particular 16 to 30, specifically 18 to 24, carbonatoms with a C₁₂-C₃₆-alkanol. The alkanols suitable for theesterification are preferably saturated, linear and mono- to dihydric,in particular monohydric. They have 12 to 36, in particular 16 to 30,specifically 18 to 24, carbon atoms. It is also possible to use mixturesof alkyl esters of alkanoic acids. Suitable examples of alkyl esters ofalkanoic acids are palmityl palmitate, stearyl stearate, arachylarachate, behenyl behenate and lignoceryl lignocerate. Preferred estersof C₁₂-C₃₆-alkanecarboxylic acids with C₁₂-C₃₆-alkanols are behenylbehenate and stearyl stearate and mixtures thereof.

In one preferred embodiment, component B comprises at least one of theabove-described esters of alkanecarboxylic acids with polyglycerol (alsoreferred to below as polyglycerol esters), in particular at least one ofthe polyglycerol esters stated as being preferred or particularlypreferred. In one preferred embodiment, component B comprises at leastone of the above-described polyglycerol esters which is obtainable byesterification of the above-described polyglycerol with at least onesaturated carboxylic acid having 18 to 24 carbon atoms, where thecarboxylic acid is selected in particular from palmitic acid, stearicacid and behenic acid and mixtures thereof. In one particularlypreferred embodiment, component B comprises at least one of theabove-described polyglycerol esters which is obtainable byesterification of behenic acid with a polyglycerol mixture consisting of0 to 10% by weight of glycerol, 15 to 40% by weight of diglycerol, 30 to55% by weight of triglycerol, 10 to 25% by weight of tetraglycerol, 0 to15% by weight of pentaglycerol, 0 to 10% by weight of hexaglycerol and 0to 5% by weight of more highly condensed polyglycerols.

In one preferred embodiment, component B consists to at least 80% byweight, in particular to at least 90% by weight, specifically to atleast 95% by weight, based on the total weight of component B, orexclusively of at least one of the above-described polyglycerol esters,in particular at least one of the polyglycerol esters stated as beingpreferred or particularly preferred. In one particularly preferredembodiment, component B consists to at least 80% by weight, inparticular to at least 90% by weight, specifically to at least 95% byweight, based on the total weight of component B, or exclusively of atleast one of the above-described polyglycerol esters which is obtainableby esterification of the above-described polyglycerol with at least onesaturated carboxylic acid having 18 to 24 carbon atoms, where thecarboxylic acid is selected in particular from palmitic acid, stearicacid and behenic acid and mixtures thereof. In one particularlypreferred embodiment, component B consists to at least 80% by weight, inparticular to at least 90% by weight, specifically to at least 95% byweight, based on the total weight of component B, or exclusively of atleast one of the above-described polyglycerol esters which is obtainableby esterification of behenic acid with a polyglycerol mixture consistingof 0 to 10% by weight of glycerol, 15 to 40% by weight of diglycerol, 30to 55% by weight of triglycerol, 10 to 25% by weight of tetraglycerol, 0to 15% by weight of pentaglycerol, 0 to 10% by weight of hexaglyceroland 0 to 5% by weight of more highly condensed polyglycerols.

According to the invention, the fraction of component B in the oil phaseis 1 to 10% by weight, preferably 2 to 8% by weight, in particular 3 to6% by weight, based on the total weight of the oil phase.

Component C present in the oil-in-water emulsions according to theinvention is one or more organic substances which are liquid at 50° C.and 1013 mbar, at atmospheric pressure have a boiling point above 200°C., e.g. in the range from 200 to 400° C., in particular of at least250° C., and which at 25° C. and 1013 mbar are essentially insoluble inwater, i.e. have a solubility in water of less than 0.1 g/l. Suitablesubstances are hydrocarbons and triglycerides of fatty acids, inparticular those having 12 to 22 carbon atoms. Component C preferablyconsists to at least 80% by weight, in particular 90% by weight,specifically 95% by weight, based on the total weight of component C, ofone or more hydrocarbons, which are in particular nonaromatic, i.e.aliphatic or cycloaliphatic, and have a boiling point of at least 200°C., preferably at least 250° C., e.g. in the range from 200 to 400° C.or 250 to 400° C. at 1.013 bar, such as, for example, liquid paraffins,white oils, soft paraffins or other standard commercial mineral oils.

According to the invention, the fraction of component C in the oil phaseis 10 to 49% by weight, preferably 20 to 40, in particular 25 to 35% byweight, based on the total weight of the oil phase.

To stabilize the oil phase in the aqueous emulsion, the emulsionsaccording to the invention advantageously comprise at least onesurface-active substance. The emulsions according to the inventioncomprise the at least one surface-active substance generally in anamount from 0.1 to 10% by weight, in particular in an amount from 0.5 to5% by weight, based on the oil phase.

Suitable surface-active substances are, in principle, all substancesknown for the stabilization of hydrophobic particles or droplets inaqueous systems, e.g. anionic, cationic, amphoteric and/or nonionicemulsifiers, and also water-soluble ionic and nonionic polymers,preferably ionically amphiphilic copolymers which have cationic oranionic groups and whose molecular weight, in contrast to theemulsifiers, is usually above 1000 daltons. Surface-active substancesare sufficiently known to the person skilled in the art, e.g. fromUllmann's Encyclopedia of Industrial Chemistry, 5th ed. vol. A9, pp.297-339.

Examples of Suitable Anionic Emulsifiers are

salts, in particular sodium and ammonium salts, of higher fatty acids,salts, in particular the sodium and ammonium salts, of sulfatedethoxylation products of C₆-C₂₂-alkylphenols, such as nonylphenol oroctylphenol,salts, in particular the sodium and ammonium salts, ofC₄-C₂₂-alkylarylsulfonates,salts, in particular the sodium and ammonium salts, of sulfonates ofnaphthalene,salts, in particular the sodium and ammonium salts, of sulfonatedC₈-C₂₂-alkyldiphenyl oxides, in particular of bis-sulfonatedC₈-C₂₂-alkyldiphenyl oxides, such as bis-sulfonated dodecyldiphenyloxide,salts, in particular the sodium and ammonium salts, ofnaphthalenesulfonic acid-formaldehyde condensates or naphthalenesulfonicacid-formaldehyde-urea condensates,and also salts, in particular the sodium and ammonium salts, ofdi-C₄-C₂₀-alkyl sulfosuccinates.

Examples of Suitable Nonionic Emulsifiers are:

alkoxylated C₆-C₂₂-alkylphenols with a degree of ethoxylation ofpreferably in the range from 5 to 50,ethoxylated unsaturated oils such as reaction products of castor oilwith 30 to 40 mol equivalents of ethylene oxide, andadduct formation products of ethylene oxide and/or propylene oxide withaliphatic alcohols having as a rule 12 to 20 carbon atoms, e.g. withfatty alcohols, with polyhydric alcohols, with amines, and also withcarboxylic acids.

The emulsions according to the invention preferably comprise at leastone emulsifier, in particular at least one anionic emulsifier in anamount of from 0.1 to 10% by weight, in particular in an amount of from0.5 to 5% by weight, based on the oil phase. In one specific embodiment,the emulsions according to the invention comprise at least one anionicemulsifier selected from the salts, in particular the sodium andammonium salts, of sulfated ethoxylation products ofC₆-C₂₂-alkylphenols.

Examples of surface-active anionic polymers are homopolymers of acrylicacid, homopolymers of methacrylic acid, copolymers of acrylic acid andmethacrylic acid in any desired molar ratio, copolymers of acrylic acidand maleic acid in any desired molar ratio, copolymers of methacrylicacid and maleic acid, polyvinylsulfonic acid,polyacrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid,copolymers of acrylic acid and acrylamide or methacrylamide, copolymersof methacrylic acid and acrylamide or methacrylamide, or the alkalimetal and ammonium salts of the specified polymers with molar masses of,for example, 1500 to 300 000.

Preferred anionic surface-active polymers are amphiphilic copolymerscomprising acid groups and comprising, in copolymerized form,

-   (a) hydrophobic monoethylenically unsaturated monomers and-   (b) monoethylenically unsaturated carboxylic acids,    monoethylenically unsaturated sulfonic acids, monoethylenically    unsaturated phosphonic acids or mixtures thereof,    and optionally monomers (c) different therefrom, and also the salts,    in particular the sodium and the ammonium salts, of such copolymers.

Examples of hydrophobic monoethylenically unsaturated monomers are:styrene, methylstyrene, ethylstyrene, acrylonitrile, methacrylonitrile,C₂- to C₁₈-olefins, esters of monoethylenically unsaturated C₃- toC₅-carboxylic acids and monohydric alcohols, vinyl alkyl ethers, vinylesters or mixtures thereof. From this group of monomers, preference isgiven to using isobutene, diisobutene, styrene and acrylic acid esterssuch as ethyl acrylate, isopropyl acrylate, n-butyl acrylate andsec-butyl acrylate.

Examples of monomers (b) are: acrylic acid, methacrylic acid, maleicacid, maleic anhydride, fumaric acid, itaconic acid, vinylsulfonic acid,2-acrylamidomethylpropane-sulfonic acid, acrylamidopropane-3-sulfonicacid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate,styrenesulfonic acid, vinylphosphonic acid or mixtures thereof, withpreference being given to acrylic acid, methacrylic acid and maleic acidand also their anhydride.

The molar mass of the amphiphilic copolymers is generally 1000 to 100000 and is preferably in the range from 1500 to 10 000. The acid numbersof the anionic amphiphilic copolymers are generally 50 to 500,preferably 150 to 350 mg of KOH/g of polymer.

Suitable surface-active polymers for stabilizing the compositionsaccording to the invention are also:

-   -   graft polymers of 5 to 40 parts by weight of N-vinylformamide        per 100 parts by weight of a polyalkylene glycol with a molar        mass of from 500 to 10 000,    -   zwitterionic polyalkylenepolyamines,    -   zwitterionic polyethyleneimines,    -   zwitterionic polyetherpolyamines or    -   zwitterionic crosslinked polyalkylenepolyamines.

Graft polymers of N-vinylformamide on polyalkylene glycols aredescribed, for example, in WO-A-96/34903. The grafted-on vinylformamideunits may optionally be up to 10% hydrolyzed. The fraction of grafted-onvinylformamide units is preferably 20 to 40% by weight, based onpolyalkylene glycol. Preference is given to using polyethylene glycolswith molar masses of from 2000 to 10 000.

Zwitterionic polyalkylenepolyamines and zwitterionic polyethyleneiminesare known, for example, from EP-B 112592. Such compounds are obtainable,for example, by firstly alkoxylating a polyalkylenepolyamine orpolyethyleneimine, e.g. with ethylene oxide, propylene oxide, and/orbutylene oxide, and then quaternizing the alkoxylation products, e.g.with methyl bromide or dimethyl sulfate, and then sulfating thequaternized alkoxylated products with chlorosulfonic acid or sulfurtrioxide. The molar mass of the zwitterionic polyalkylenepolyamines is,for example, 1000 to 9000, preferably 1500 to 7500. The zwitterionicpolyethyleneimines preferably have molar masses in the range from 2000to 1700 daltons.

The compositions according to the invention preferably comprise at leastone anionic surface-active substance. This is preferably selected fromthe aforementioned anionic emulsifiers, the aforementionedacid-carrying, water-soluble polymers and mixtures thereof.

For the stability of the emulsions according to the invention, it hasproven advantageous if they comprise 0.05 to 8% by weight, in particular0.1 to 5% by weight, based on the oil phase, of at least one acid-havingwater-soluble homo- or copolymer, preferably of a salt thereof andoptionally at least one anionic emulsifier. The emulsifiers arepreferably likewise used in an amount of from 0.05 to 5% by weight,based on the total weight of the oil phase. In particular, thoseemulsions which comprise at least one anionic emulsifier and at leastone of the aforementioned acid-carrying water-soluble polymers areadvantageous.

Besides the oil phase, the emulsions according to the invention cancomprise, as further disperse constituent, finely divided, virtuallywater-insoluble, inert solids with particle sizes (weight-averageparticle diameter) below 20 μm, preferably in the range from 0.1 to 10μm. If desired, the emulsion according to the invention comprises thesefurther inert solids in an amount of, for example, 0.1 to 50% by weight,preferably 1 to 35% by weight, based on the weight of the oil phase ofthe oil-in-water emulsions. Suitable inert solids are in particularinorganic solids such as e.g. kaolin, chalk, bentonite, talc, bariumsulfate, silicon dioxide, zeolites, but also organic solids such asurea-formaldehyde pigments, melamine-formaldehyde pigments andmicrocrystalline cellulose, where the inert inorganic solids may also behydrophobized, e.g. by treatment with trialkylsilyl halides. In contrastto the oil phase, these inert solids are solid at a temperature of 100°C. In one preferred embodiment of the invention, the emulsions compriseno finely divided, virtually water-insoluble, inert solids differentfrom components A, B and C.

As a rule, the solids content of the oil-in-water emulsion according tothe invention is in a range from 10 to 50% by weight, in particular 15to 45% by weight, specifically 20 to 40% by weight, based on the totalweight of the oil-in-water emulsion.

The emulsions according to the invention frequently comprise one or morethickeners for setting the viscosity required for the respectiveapplication. In principle, it is possible to use all thickeners knownfor thickening oil-in-water systems. These include natural thickenerssuch as polysaccharides, carrageenates, Tragacanth, alginates, starch,caseinates, modified organic polymers such as carboxymethylcellulose,synthetic thickeners such as polyacrylic acids, polyvinyl alcohol,polyethylene glycols, polyacrylamides, and, in particular, copolymers ofacrylamide with ethylenically unsaturated carboxylic acids, inparticular with acrylic acid, and optionally with comonomers. Thesethickeners are described in EP-A 149 812, the disclosure of which ishereby referred to. Further suitable thickeners are mentioned in theoverview article by Warren. B. Shapiro, Oil-in Water-Emulsions,Cosmetics & Toiletries, vol. 97, 1982, 27-33. Particular preference isalso given to so-called associative thickeners, e.g. hydrophobicallymodified polyurethanes, hydrophobically modified cellulose ethers, whichbuild up high molecular weight network structures in accordance with theprinciple of hydrophobic interaction in aqueous phase. Associativethickeners are known to the person skilled in the art, e.g. J.Bielemann, Additives for Coatings, Wiley-VCH Weinheim 2000 and arecommercially available, e.g. under the names RHOPLEX® and PRIMAL® TT 935from Rohm & Haas, USA. In one preferred embodiment of the invention, theemulsions comprise no thickener.

In addition, the emulsions according to the invention also frequentlycomprise commercially available biocides for preservation, e.g.formaldehyde, isothiazolinone compounds such as the products sold byArch Chemicals under the name PROXEL® and the products sold by ThorChemie GmbH under the name ACTICIDE®.

To prepare the emulsion according to the invention, as a rule the oilphase is emulsified in the aqueous phase. For this, a melt of componentsA, B and C of the oil phase will usually be incorporated, i.e.emulsified, into an aqueous phase which optionally comprises one or moresurface-active substances. The incorporation and/or emulsificationgenerally takes place at temperatures above the melting point of the oilphase, e.g. at temperatures in the range from 55 to 100° C. Theincorporation takes place in a manner known per se for producingemulsions by using apparatuses such as e.g. dispersing devices, in whichthe components of the emulsion are subjected to a considerable sheargradient. In order to obtain particularly stable oil-in-water emulsions,the emulsification of the oil phase in the aqueous phase is preferablycarried out in the presence of surface-active substances.

Emulsifying the oil phase in the aqueous phase gives oil-in-wateremulsions. Immediately after preparation, these generally have aviscosity in the range from 300 to 3000 mPa·s (determined in accordancewith Brookfield at 25° C., e.g. with spindle 4 at 20 revolutions perminute).

The average particle size (weight average of the droplet diameter) ofthe oil-in-water emulsion is generally below 25 μm, preferably in therange from 0.1 to 15 μm, in particular 0.5 to 10 μm, determined by meansof light scattering at 20° C.

The oil-in-water emulsions according to the invention can be used asantifoams and/or deaerators for controlling foam and/or deaeration ofaqueous media, for example in the food industry, the starch industry, inwaste treatment plants or in the paper industry. Preference is given totheir use as borehole solution and in the paper industry, in particularduring pulp cooking, pulp washing, the grinding of paper stock,papermaking and the dispersion of pigments for papermaking.Specifically, the oil-in-water emulsions according to the invention areused in the paper industry as deaerators of paper stock suspensions.Particular preference is given here to the use as deaerators of theheadbox in papermaking.

As antifoams or deaerators, the oil-in-water emulsions are generallyused in amounts of from 0.01 to 2 parts by weight per 100 parts byweight of the foam-forming aqueous liquid, preferably in amounts of from0.02 to 1 part by weight per 100 parts by weight of the foam-formingliquid, in particular in amounts of from 0.05 to 0.5 parts by weight per100 parts by weight of the foam-forming liquid.

The advantages of the emulsions according to the invention are evidentparticularly at temperatures in the range from 20 to 50° C.

The examples below are intended to illustrate the invention in moredetail and are not to be understood as being limiting.

Physicochemical Test Methods

The average particle size (weight-average particle diameter d₅₀) of theparticles of the oil phase emulsified in water was determined with thehelp of a Coulter counter from Beckmann.

The viscosity was determined using a Brookfield rotary viscometer modelRVT, spindle 4 at 20 revolutions per minute at 25° C.

The solids content was determined by back-weighing the samples followingstorage in a drying cabinet at 110° C. to constant weight.

The average air content was determined by pumping in each case 101 of afoam-developing paper stock suspension 0.1% (groundwood) in a containermade of a transparent plastic for 5 minutes. The amount of air formed inthe stock suspension was then ascertained using an air measuring device(e.g. based on impedance methods as in the case of the Sonica devicefrom Conrex or based on sonic speed measurements as in the case ofSonatrac from Cidra). To assess the effectiveness of a deaerator, theaverage air content was stated 5 minutes after adding the deaerator.

If the paper suspension is pumped round in the absence of an antifoamfor 5 minutes, then an average air content of 4% by volume is obtained.By adding in each case 5 mg/l of an effective deaerator to the paperstock suspension, this value is significantly reduced, meaning that itis a measure of the effectiveness of a deaerator.

After testing, the temperature of the paper stock suspension in eachcase was 30 or 40° C., the temperature being kept constant to +/−1° C.during the 5 minute test. In this terminology, the more effective theantifoam, the lower the average air content in the paper stocksuspension.

The parts stated in the examples are parts by weight.

The C_(16/18)-fatty alcohol used below as component A consists to 32% byweight of a linear C₁₆-alcohol, to 67% by weight of a linear C₁₈-alcoholand to 1% by weight of a linear C₂₀-alcohol. The melting range of thismixture is 51 to 52° C.

The C₂₀₊-alcohol used in the comparative examples as component Aconsisted of 3% by weight of a linear C₁₈-alcohol, 45% by weight of alinear C₂₀-alcohol, 25% by weight of a linear C₂₂-alcohol, 15% by weightof a linear C₂₄-alcohol and 12% by weight of higher alcohols. Themelting range of this mixture was 45° C. to 54° C.

The polyglycerol ester used as component B was prepared by esterifying apolyglycerol mixture consisting of 27% diglycerol, 44% triglycerol, 19%tetraglycerol and 10% more highly condensed polyglycerols with behenicacid. The degree of esterification was 60%.

The hydrocarbon (paraffin) used as component C has a melting point of38° C.

The surface-active substances used were:

sodium salt of the sulfuric acid half-ester of isooctylphenolethoxylated with 25 mol/mol of ethylene oxide as anionic emulsifier;anionic copolymer of 70% by weight of acrylamide and 30% by weight ofacrylic acid with a K value of 270.

EXAMPLE 1

The components of the oil phase were firstly heated to a temperature of110° C. and then incorporated into the aqueous phase heated to 80° C. bymeans of a dispersing device.

The oil phase had the following composition, based on the total weightof the emulsion:

-   -   20 parts of the C_(16/18)-fatty alcohol,    -   9 parts of paraffin and    -   1 part of polyglycerol ester.

The water phase consisted, based on the total weight of the emulsion,of:

-   -   68.3 parts of water,    -   1 part of the anionic emulsifier,    -   0.5 part of the anionic copolymer and    -   0.2 part of sodium hydroxide solution.

The physical properties and the deaerating effect of this emulsion aregiven in table 2.

The examples and comparative examples given in table 1 were prepared inan analogous manner. The quantitative data are % by weight, based on thetotal weight of the emulsion. The composition of the water phasecorresponded in all examples to the water phase of example 1. Thephysical properties and the deaerating effect of this emulsion are givenin table 2.

TABLE 1 Example Component 1 2 3 4 5 C1 C2 C3 C4 C_(16/18)-fatty 20  20 20  20  17.5 20 20 10 10  alcohol C₂₀₊-alcohol — — — — 2.5 — — 10 5Polyglycerol 1 — 1 — 1 — —  1 1 ester Behenyl — 3 — 3 — — — — — behenateParaffin 9 7 — — 9 — 10  9 9 Palm oil — — 9 7 — 10 — — —

TABLE 2 Physical properties and deaerating effect of the antifoamsAverage particle Viscosity Solids content Air content [%] size [μm] [mPa· s] [%] 30° C. 40° C. 1 2.1 420 29.8 0.1 0.1 2 2.2 470 29.9 0.1 0.1 32.1 450 29.7 0.2 0.2 4 2.0 490 29.8 0.2 0.2 5 2.3 440 29.9 0.3 0.2 C12.2 390 29.7 0.8 1.0 C2 2.2 420 29.8 1.0 1.2 C3 2.6 360 29.8 0.5 0.4 C42.3 390 29.9 0.4 0.4

1: An oil-in-water emulsion, comprising: an oil phase, wherein the oilphase comprises at least 95% by weight of from 50 to 80% by weight,based on a total weight of the oil phase, of an alkanol having at least16 carbon atoms, wherein a fraction of the alkanol having 16 to 18carbon atoms comprises at least 80% by weight, based on a total amountof the alkanol; from 1 to 10% by weight, based on the total weight ofthe oil phase, of at least one ester selected from the group consistingof a C₁₂-C₃₆-alkanecarboxylic acid with polyglycerol and of aC₁₂-C₃₆-alkanecarboxylic acid with a C₁₂-C₃₆-alkanol; and from 10 to 49%by weight, based on the total weight of the oil phase, of an organicsubstance, wherein the organic substance is liquid at 50° C. and 1013mbar, at atmospheric pressure the organic substance has a boiling pointabove 200° C., and at 25° C. and 1013 mbar the organic substance has asolubility in water of less than 0.1 g/l. 2: The oil-in-water emulsionaccording to claim 1, wherein the alkanol consists essentially ofunbranched alkanols. 3: The oil-in-water emulsion according to claim 1,wherein the alkanol comprises at least 80% by weight of at least onealkanol is selected from the group consisting of palmityl alcohol andstearyl alcohol. 4: The oil-in-water emulsion according to claim 1,wherein the at least one ester is at least 80% by weight from the estercomprising a C₁₈-C₂₄-alkanecarboxylic acid with polyglycerol. 5: Theoil-in-water emulsion according to claim 4, whereinpolyglycerol-comprising ester is obtained by esterification ofpolyglycerol with behenic acid. 6: The oil-in-water emulsion accordingto claim 1, wherein the organic substance comprises at least 80% byweight of an aliphatic hydrocarbon oil. 7: The oil-in-water emulsionaccording to claim 1, wherein a solid content of the oil-in-wateremulsion is of from 10 to 50%. 8: The oil-in-water emulsion according toclaim 1, wherein a weight-average particle size of the oil-in-wateremulsion is of from 0.5 to 10 μm. 9: A method for producing an antifoamor deaerator in an aqueous composition, comprising: producing theantifoam or deaerator with the oil-in-water emulsion according toclaim
 1. 10: A method for producing a deaerator for an aqueous paperstock suspension, comprising: producing the deaerator for the aqueouspaper stock suspension with the oil-in-water emulsion according toclaim
 1. 11: A method for producing a deaerator in a headbox ofpapermaking comprising: producing the deaerator in the headbox ofpapermaking with the oil-in-water emulsion according to claim
 1. 12: Amethod of employing the oil-in-water emulsion according to claim 8,comprising: employing the oil-in-water emulsion at a temperature of from20 to 50° C. 13: The method according to claim 9, wherein the producingis producing at a temperature of from 20 to 50° C. 14: The methodaccording to claim 10, wherein the producing is producing at atemperature of from 20 to 50° C. 15: The method according to claim 11,wherein the producing is producing at a temperature of from 20 to 50° C.